1. Field of the Invention
The present invention relates to a system for regional and local supervision and monitoring of elevator equipment.
2. Description of Related Art
An example of previously known technology is found in U.S. Pat. No. 3,973,648, which presents an apparatus for monitoring elevator groups by means of a central computer and a modem link. The central computer selects an elevator group, which then returns digital data in serial form about events relating to the operation, disturbances and alarms in the elevator group. For communication between the elevator group and the central computer, the apparatus is provided with a hardware interface used for monitoring and transmission.
A drawback with the system is that the data are transmitted in an undecoded form. The central computer must decode the received data and decide whether the decoded information has resulted in service operations. For the transmission of up-to-date data to the central computer, rented communication lines have to be resereved for a long time and a lot of computer time is required. Another drawback is that the central computer calls the elevator groups to be monitored. Therefore, the information is not obtained at the instant it is generated but only after a delay depending on the inquiry period. Besides, at least during periods of a low traffic volume, it is possible that no events are registered.
For the installation of the car equipment, several car cable wires between the elevator car and the telephone interface unit placed in the machine room are needed for voltage supply, signal light control, monitoring of switches and push buttons and for the control of the speaker and microphone. Most car cables, especially those of old elevators, do not have a sufficient number of extra wires in well-protected conductor pairs. It is necessary to install a new car cable which meets the requirements of the connection.